The present disclosure relates generally to surgical systems and in particular automated and computerized surgical systems. Although specific reference is made to laser eye surgery systems, the methods and apparatus described herein can be used with many different automated surgical systems for a variety of surgical procedures.
Many surgical procedures can be performed on patients, including ophthalmic surgery. Opthalmic surgery can include surgery on one or more of the cornea, the lens or the retina, for example.
Cataract extraction is a frequently performed surgical procedure. A cataract is formed by opacification of the crystalline lens or its envelope—the lens capsule—of the eye. The cataract obstructs passage of light through the lens. A cataract can vary in degree from slight to complete opacity. Early in the development of an age-related cataract the power of the lens may be increased, causing near-sightedness (myopia). Gradual yellowing and opacification of the lens may reduce the perception of blue colors as those wavelengths are absorbed and scattered within the crystalline lens. Cataract formation typically progresses slowly resulting in progressive vision loss. Cataracts are potentially blinding if untreated.
A common cataract treatment involves replacing the opaque crystalline lens with an artificial intraocular lens (IOL). An estimated 15 million cataract surgeries per year are performed worldwide. The cataract treatment market is composed of various segments including intraocular lenses for implantation, viscoelastic polymers to facilitate surgical procedures, and disposable instrumentation including ultrasonic phacoemulsification tips, tubing, various knives, and forceps.
Cataract surgery is typically performed using a technique termed phacoemulsification in which an ultrasonic tip with associated irrigation and aspiration ports is used to sculpt the relatively hard nucleus of the lens to facilitate removal through an opening made in the anterior lens capsule. The nucleus of the lens is contained within an outer membrane of the lens that is referred to as the lens capsule. Access to the lens nucleus can be provided by performing an anterior capsulotomy in which a small (often round) hole is formed in the anterior side of the lens capsule. Access to the lens nucleus can also be provided by performing a manual continuous curvilinear capsulorhexis (CCC) procedure. After removal of the lens nucleus, a synthetic foldable intraocular lens (IOL) can be inserted into the remaining lens capsule of the eye. Typically, the IOL is held in place by the edges of the anterior capsule and the capsular bag. The IOL may also be held by the posterior capsule, either alone or in unison with the anterior capsule. This latter configuration is known in the field as a “Bag-in-Lens” implant.
One of the most technically challenging and critical steps in the cataract extraction procedure is providing access to the lens nucleus. The manual continuous curvilinear capsulorhexis (CCC) procedure evolved from an earlier technique termed can-opener capsulotomy in which a sharp needle was used to perforate the anterior lens capsule in a circular fashion followed by the removal of a circular fragment of lens capsule typically in the range of 5-8 mm in diameter. The smaller the capsulotomy, the more difficult it is to produce manually. The capsulotomy provides access for the next step of nuclear sculpting by phacoemulsification. Due to a variety of complications associated with the initial can-opener technique, attempts were made by leading experts in the field to develop a better technique for removal of the circular fragment of the anterior lens capsule prior to the emulsification step.
The desired outcome of the manual continuous curvilinear capsulorhexis is to provide a smooth continuous circular opening through which not only the phacoemulsification of the nucleus can be performed safely and easily, but also to provide for easy insertion of the intraocular lens. The resulting opening in the anterior lens capsule provides access for tool insertion during removal of the nucleus and for IOL insertion, a permanent aperture for transmission of the image to the retina of the patient, and also support of the IOL inside the remaining lens capsule that limits the potential for dislocation. The resulting reliance on the shape, symmetry, uniformity, and strength of the remaining lens capsule to contain, constrain, position, and maintain the IOL in the patient's eye limits the placement accuracy of the IOL, both initially and over time. Subsequently, a patient's refractive outcome and resultant visual acuity are less deterministic and intrinsically sub-optimal due to the IOL placement uncertainty. This is especially true for astigmatism correcting (“toric”) and accommodating (“presbyopic”) IOLs.
Problems may also develop related to inability of the surgeon to adequately visualize the lens capsule due to lack of red reflex, to grasp the lens capsule with sufficient security, and to tear a smooth circular opening in the lens capsule of the appropriate size and in the correct location without creating radial rips and extensions. Also present are technical difficulties related to maintenance of the depth of the anterior chamber depth after opening the lens capsule, small pupils, or the absence of a red reflex due to the lens opacity. Some of the problems with visualization can be minimized through the use of dyes such as methylene blue or indocyanine green. Additional complications may also arise in patients with weak zonules (typically older patients) and very young children that have very soft and elastic lens capsules, which are very difficult to controllably and reliably rupture and tear.
The implantation of a “Bag-in-Lens” IOL typically uses anterior and posterior openings in the lens capsule of the same size. Manually creating matching anterior and posterior capsulotomies for the “Bag-in-Lens” configuration, however, is particularly difficult.
Many patients have astigmatic visual errors. Astigmatism can occur when the corneal curvature is unequal in two or more directions. In Astigmatic Keratotomy, Corneal Relaxing Incision (CRI), and Limbal Relaxing Incision (LRI), corneal incisions are made in a well-defined manner and depth to allow the cornea to change shape to become more spherical. These corneal incisions can accomplished manually but often with limited precision.
Although prior laser eye surgical systems have been designed to overcome some of the above challenges, these prior surgery systems may be less than ideal in at least some respects and can provide less than ideal results in at least some instances. Although the prior laser eye surgery systems have attempted to automate laser corneal incisions and provide visualization of the eye, such systems can be somewhat cumbersome and more complex than would be ideal. For example, the prior laser eye surgery systems may comprise several subsystems that communicate and coordinate with each other and can be susceptible to noise and crosstalk in at least some instances. Also, the power consumption and size of these systems may also be greater than would be ideal in at least some instances, such that improved laser eye surgery may not be available to many people who could benefit from the therapies provided by these systems.
In many prior laser surgery systems, the effectiveness of the signaling can be dependent on the length of the signaling wire and its capacitance, and proximity to other wires, such that the signaling can be susceptible to noise and cross talk. Noise, crosstalk, and other electronic signaling defects may lead to errors and miscommunications between subsystems in at least some instances, and can reduce the safety, reliability, and precision of the surgical system and procedures the system performs, such that the outcome of the surgical procedure may be less than ideal.
Thus, improved surgical systems with improved communications between its subsystems are desired so that laser eye surgery procedures can be more reliably and safely performed and available to more patients.